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applied physiology > muscle structure and function Pt 1 - Week 4 > Flashcards

muscle structure and function Pt 1 - Week 4 Flashcards

1
Q

what are the 4 functions of the muscles ?

A

force production for locomotion and breathing

force production for postural support

heat production during cold stress

acts as an endocrine organ

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2
Q

what is the epimysium ?

A

surrounds entire muscle

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3
Q

what is the perimysium?

A

surround fascicles

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4
Q

what is the endomysium ?

A

surrounds muscle fibres

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5
Q

what is the basement membrane ?

A

just below endomysium

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6
Q

what is the sarcolemma ?

A

muscle cell membrane

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7
Q

what are the myofibrils ?

A

contractile proteins

actin - thin filament

myosin - thick filament

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8
Q

what are the sarcomeres? (4)

A

z line - space between sarcomere unit

M lines - middle of sarcomere

A band - crossover between actin and myosin

I band - no cross over between actin and myosin filament

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9
Q

what is the sarcoplasmic reticulum ? (3)

A

muscles wrapped in the sarcolemma

storage sites for calcium

terminal cisternae

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10
Q

what are transverse tubules(2)

A

extend from sarcolemma to sarcoplasmic reticulum

help signal from periphery get deeper so that all fibres will contract

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11
Q

what is role of satellite cells ?

A

increase No. nuclei in mature muscle fibres - help growth and repair

myonuclear domain

more myonuclei allow greater protein synthesis
- muscle hypertrophy

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12
Q

what is importance of myonuclear domain and how does training effect it ? (2)

A

responsible for gene expression for surround sarcoplasm

training causes hypertrophy which recruits satellite cells to increase muscle fibres

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13
Q

What is a neuromuscular junction ?

A

Junction between motor neurons and muscle fibres

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14
Q

What is a motor end plate?

A

Pocket formed around motor neuron by sarcolemma

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15
Q

What is a neuromuscular cleft?

A

Short gap between neuron and muscle fibre

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16
Q

What is the role of acetylcholine in NMJ?

A

Stimulates the muscle fibre to depolarise, causing the signal to start the contractile process

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17
Q

Why does muscle shortening occur ?

A

Movement of actin filament over myosin filament

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18
Q

What’s is the cross bridge formation ?

A

Actin and myosin create a power stroke

19
Q

Tropomyosin is found where ?

A

Calcium binding site

20
Q

Where does the head of myosin attach ?

A

Actin binding site

21
Q

Myosin : thick or thin filaments ?

A

Thick

22
Q

Actin : thick or thin filament ?

A

Thin

23
Q

The release of energy from ATP hydrolysis creates energy required for..?

A

Power stroke

24
Q

___ ATPase breaks down ____ as fibre contracts

A

Myosin

ATP

25
Q

What are sources of ATP ? (3)

A

Phosphocreatine

Glycolysis

Oxidative phosphorylation

26
Q

Explain the repeated contraction cycle (4)

A

ATP binds to myosin head

ATP hydrolysed and binds to actin

Releases phosphate and ADP - causes power stroke where filaments slide over one another

ATP needs to be replenished to repeat cycle

27
Q

During excitation-contraction coupling where does the signal from the motor nerve enter ? (3)

A

Synaptic knob

Through transverse tubules

To the sarcoplasmic reticulum

28
Q

During excitation-contraction coupling what is released to receptors on sarcolemma of muscle fibre ?

A

Synaptic vesicles release acetylcholine across synaptic cleft

29
Q

During excitation-contraction coupling, what does the release of ACh cause ?

A

Excitation of muscle fibre which leads to depolarisation

30
Q

During excitation-contraction coupling, what does depolarisation cause ?

A

Opens calcium ion channels from sarcoplasmic reticulum

31
Q

During excitation-contraction coupling, what do calcium ions bind to and what does this cause ?

A

Troponin on actin molecules

Causes tropomyosin to move away from ‘active sites’ on the actin molecule for a strong binding site for actin + myosin

32
Q

During excitation-contraction coupling what happens to energised myosin crossbridges?

A

Binds to active site on actin and pulls on actin to produce back and forth movement

33
Q

During excitation-contraction coupling, once the back and forth movement is created what happens to ACh with the muscle fibre and Calcium ?(2)

A

ACh release stops and muscle is repolarised

Calcium is pumped from cytosol into sarcoplasmic reticulum

34
Q

What is fatigue ?

A

Decline in muscle power output

35
Q

What is muscle fatigue(decline in muscle power output) caused by ? (3)

A

Decrease in force production at cross bridge level

Decrease in muscle shortening velocity

Also depends on exercise intensity

36
Q

What is the lactate threshold for moderate, heavy and very heavy exercise ?

A

Moderate:50 -75% (up to 60% VO2 max)

Heavy: 76-85% ( 60-75 VO2 max)

Very heavy: 86- 100% (76-100 VO2 max)

37
Q

What are possible causes of fatigue for max intensity exercise ? (2)

A

Decrease in Ca2+ release form sarcoplasmic reticulum

Accumulation of metabolites inhibiting myofilament sensitivity

38
Q

What are the key metabolites contributing to fatigue at max intensity ? (3)

A

Pi , H+ , free radicals

Pi + free radicals modify cross bridge head + reduce No. bridges bound to actin

H+ bind to Ca2+ binding sites on troponin to prevent Ca2 binding and contraction

39
Q

What are the possible causes for fatigue for moderate intensity exercise? (2)

A

Increased radical production

Glycogen depletion

40
Q

What are the key metabolites that contribute to fatigue during moderate intensity exercise ? (3)

A

Accumulation of Pi and H+ don’t contribute to fatigue

Radical accumulation modifies cross-bridge head and reduce number of cross bridges bound to actin

Depletion of muscle glycogen stores reduce TCA cycle intermediates + decrease ATP production via oxidative phosphorylation

41
Q

What are EAMCs cramps?

A

Exercise associated muscle cramps

Spasmodic , involuntary muscle contractions during exercise

Associated with prolonged high intensity exercise

42
Q

What is the myth about EAMCs?

A

EAMCs aren’t caused by electrolyte imbalance or dehydration

Only likely in hot environments that cause electrolyte imbalance

43
Q

What are EAMS likely caused by ? (3)

A

Altered muscle spindle and Golgi tendon organ function

Increased excitatory activity of muscle spindles and reduced inhibitory effect of Golgi tendon organ

Hyperactive motor neurons in spinal cord

44
Q

What are strategies to alleviate EAMS ? (2)

A

Passive stretching

Activating ion channels in mouth can send inhib signals to spinal cord

applied physiology (22 decks)

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